For producing semiconductor devices, in particular silicon semiconductor devices, so-called photolithographic methods may, for instance, be used.
With these methods, the surface of a corresponding wafer—consisting of monocrystalline silicon—is subject to an oxidation process, and subsequently a light-sensitive photoresist layer is applied to the oxide layer.
Subsequently—by interconnecting an appropriate optical device—a photomask is placed above the wafer, the layout structure of which corresponds to the layout structure to be provided on the wafer—or a particular level of the wafer.
Then, the photomask—and thus also the corresponding structure on the photoresist—is exposed, and then the photomask is removed again.
When the photoresist is then developed and subject to an etching process, the exposed positions of the photoresist (and the respective positions of the oxide layer thereunder) are removed from the wafer—and the non-exposed positions are left (or—in the case of negative photoresist—in a correspondingly opposite manner the exposed positions).
Through the exposed windows, the monocrystalline silicon can now specifically be supplied with impurities, e.g. by corresponding diffusion or ion implantation processes; n-conductive regions may, for instance, be produced by the introduction of pentavalent atoms, e.g. phosphorus, and p-conductive regions may be produced by the introduction of trivalent atoms, e.g. boron.
The structures that can be put into practice by means of such photolithographic methods may range within the wavelengths of the light used for exposure.
Conventionally, for each level of the wafer (or for each level of the semiconductor devices or chips to be produced thereon, respectively) respective separate masks with respective different layout structures are used.
For the production of different chips, different mask sets have to be used.
If the chip layout is to be changed for a particular chip, new masks are needed (in particular e.g. a complete, new mask set).
This is of disadvantage especially since the production of masks is costly and expensive.